Losing Steam?

I started off my diet at 1200 calories per day. It's been 90 days, I've losing 25 pounds, and I've been losing my steam. I'm tired of dieting and logging and can rarely eat less than 1500-1700 per day. I exercise, but lose steam during that too. I've gained two pounds back in the past two weeks.

I'm also under stress going back to school, where there will be tons of options for junk food. If I'm prone to binge eating when I get there, I'm going to gain it back. But I can't stop eating, and I can't get myself motivated!

Do you guys have any advice for staying motivated? I've yoyoed before, and this feels like the point where the weight starts to go back up.